Cavity pressure modification using local heating with a laser

ABSTRACT

A method and system for changing a pressure within at least one enclosure in a MEMS device are disclosed. In a first aspect, the method comprises applying a laser through one of the at least two substrates onto a material which changes the pressure within at least one enclosure when exposed to the laser, wherein the at least one enclosure is formed by the at least two substrates. In a second aspect, the system comprises a MEMS device that includes a first substrate, a second substrate bonded to the first substrate, wherein at least one enclosure is located between the first and the second substrates, a metal layer within one of the first substrate and the second substrate, and a material vertically oriented over the metal layer, wherein when the material is heated the material changes a pressure within the at least one enclosure.

PRIORITY CLAIM

This patent application is a divisional application that claims priorityto U.S. patent application Ser. No. 14/705,630, filed May 6, 2015,entitled “CAVITY PRESSURE MODIFICATION USING LOCAL HEATING WITH ALASER,” the entirety of which is incorporated by reference herein.

FIELD OF THE INVENTION

The present invention relates to microelectromechanical system (MEMS)sensors, and more particularly, to modifying cavity pressure of a MEMSsensor by using localized heating.

BACKGROUND

Microelectromechanical system (MEMS) sensors can have different cavitieswithin the same cap and substrate. Conventional MEMS sensors requireadditional time consuming and costly manufacturing steps to createcavities at varying pressures. In addition, conventional MEMS sensors donot enable adjustment of the cavity pressure after it has been sealed.Therefore, there is a strong need for a solution that overcomes theaforementioned issues. The present invention addresses such a need.

SUMMARY OF THE INVENTION

A method and system for changing a pressure within at least oneenclosure in a MEMS device are disclosed. In a first aspect, the methodcomprises applying a laser through one of the at least two substratesonto a material which changes the pressure within at least one enclosurewhen exposed to the laser, wherein the at least one enclosure is formedby the at least two substrates.

In a second aspect, the system comprises a MEMS device that includes afirst substrate, a second substrate bonded to the first substrate,wherein at least one enclosure is located between the first and thesecond substrates, a metal layer within one of the first substrate andthe second substrate, and a material vertically oriented over the metallayer, wherein when the material is heated the material changes apressure within the at least one enclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying figures illustrate several embodiments of the inventionand, together with the description, serve to explain the principles ofthe invention. One of ordinary skill in the art readily recognizes thatthe embodiments illustrated in the figures are merely exemplary, and arenot intended to limit the scope of the present invention.

FIG. 1 illustrates a cross-section view of a device in accordance withan embodiment.

FIG. 2 illustrates a cross-section view of a device in accordance withan embodiment.

FIG. 3 illustrates a cross-section view of a device in accordance withan embodiment.

FIG. 4 illustrates a cross-section view of a device in accordance withan embodiment.

FIG. 5 illustrates a method for changing a pressure within a device inaccordance with an embodiment.

FIG. 6 illustrates a cross-section view of a device in accordance withan embodiment.

DETAILED DESCRIPTION

The present invention relates to microelectromechanical system (MEMS)sensors, and more particularly, to modifying cavity pressure of a MEMSsensor by using localized heating. The following description ispresented to enable one of ordinary skill in the art to make and use theinvention and is provided in the context of a patent application and itsrequirements. Various modifications to the preferred embodiment and thegeneric principles and features described herein will be readilyapparent to those skilled in the art. Thus, the present invention is notintended to be limited to the embodiments shown but is to be accordedthe widest scope consistent with the principles and features describedherein.

Micro-Electro-Mechanical Systems (MEMS) refers to a class of devicesfabricated using semiconductor-like processes and exhibiting mechanicalcharacteristics such as the ability to move or deform. MEMS often, butnot always, interact with electrical signals. A MEMS device may refer toa semiconductor device implemented as a microelectromechanical system. AMEMS device includes mechanical elements and optionally includeselectronics for sensing. MEMS devices include but are not limited togyroscopes, accelerometers, magnetometers, and pressure sensors.

In MEMS devices, a port is an opening through a substrate to expose MEMSstructure to the surrounding environment. A chip includes at least onesubstrate typically formed from a semiconductor material. A single chipmay be formed from multiple substrates, wherein the substrates aremechanically bonded to preserve functionality. Multiple chips include atleast two substrates, wherein the at least two substrates areelectrically connected but do not require mechanical bonding.

Typically, multiple chips are formed by dicing wafers. MEMS wafers aresilicon wafers that contain MEMS structures. MEMS structures may referto any feature that may be part of a larger MEMS device. One or moreMEMS features comprising moveable elements is a MEMS structure. MEMSfeatures may refer to elements formed by a MEMS fabrication process suchas bump stop, damping hole, via, port, plate, proof mass, standoff,spring, and seal ring.

MEMS substrates provide mechanical support for the MEMS structure. TheMEMS structural layer is attached to the MEMS substrate. The MEMSsubstrate is also referred to as handle substrate or handle wafer. Insome embodiments, the handle substrate serves as a cap to the MEMSstructure. Bonding may refer to methods of attaching and the MEMSsubstrate and an integrated circuit (IC) substrate may be bonded using aeutectic bond (e.g., AlGe, CuSn, AuSi), fusion bond, compression,thermocompression, adhesive bond (e.g., glue, solder, anodic bonding,glass frit). An IC substrate may refer to a silicon substrate withelectrical circuits, typically CMOS circuits. A package provideselectrical connection between bond pads on the chip to a metal lead thatcan be soldered to a printed board circuit (PCB). A package typicallycomprises a substrate and a cover.

An enclosure or sealed cavity may refer to a fully enclosed volumetypically surrounding the MEMS structure and typically formed by the ICsubstrate, structural layer, MEMS substrate, and the standoff seal ring.

A method and system in accordance with the present invention enablespressure reduction within at least one enclosure of a MEMS device bylocally heating and activating a material within the at least oneenclosure at a higher temperature than feasible for the entire MEMSdevice. In one embodiment, the material is heated by applying a laserthrough one of at least two substrates that form the at least oneenclosure and onto the material which changes the pressure within the atleast one enclosure when the material is exposed to the heat produced bythe laser. The method and system reduces the manufacturing and processsteps required to create cavities with differing pressures, reducescosts, and provides better control of the desired cavity pressure ofMEMS devices.

In one embodiment, the method and system provide for changing a pressurewithin at least one enclosure of a device. The pressure can be increasedor decreased within a given cavity after the cavity has been sealed.Therefore, different cavities within the same cap and substrate of thedevice (e.g., a MEMS cap and MEMS substrate of a MEMS device) can havedifferent pressures even though they were previously sealed with thesame process and the same pressure.

For example, a MEMS device that is manufactured with three sealedcavities with the same pressure can be modified using a method inaccordance with the present invention to have a first cavity with afirst pressure (the original pressure), a second cavity with a secondpressure, and a third cavity with a third pressure, wherein the secondpressure is lower than the first pressure and the third pressure ishigher than the first pressure. The method provides a simpler processfor multiple cavities with different pressures by reducing processsteps.

By initially manufacturing/creating a device with a plurality ofcavities that all have the same pressure, and then changing the pressureof at least a portion of the plurality of cavities after the pluralityof cavities have been sealed using a method in accordance with thepresent invention, the complexity, time, and costs associated with thedevice manufacturing process steps are reduced. Referring back to theexample above, if the device was originally created with three cavitiesthat each have different pressures before the cavities are sealed, theassociated manufacturing time and costs would be greater than if thedevice was originally created with three cavities of similar pressuresand then pressures are changed after the cavities have been sealed.

In one embodiment, the method in accordance with the present inventionprovides for local heating and outgassing for different cavities withinthe same substrate. This is advantageous for inertial sensors wheregyroscopes operating a low pressure are contained within an enclosure ofa substrate and accelerometers operating at a higher pressure arecontained in another enclosure within the same substrate. One ofordinary skill in the art readily recognizes that other MEMS devicearrangements require differing pressures within the same substrates andthat would be within the spirit and scope of the present invention.

The method and system in accordance with the present invention providefor local pressure adjustment with each cavity of a device by locallyheating a material (e.g., outgassing material, gettering/gettermaterial) within each cavity. The outgassing material outgasses(releases gas) when heated and the gettering material absorbs gas whenheated. Therefore, in one embodiment, to increase the pressure within anenclosure, the laser light/heat is applied to the outgassing material(by releasing gases into the cavity, the pressure is increased) and todecrease the pressure within an enclosure, the laser light/heat isapplied to the gettering material (by absorbing gases from the cavity,the pressure is decreased).

In addition to using a laser/light to heat the material, other heatingmethods that change the pressure while being localized and providingsimilar levels of adjustment can be utilized. In one embodiment, thelaser is an infrared (IR) laser.

To describe the features of the present invention in more detail, refernow to the following description in conjunction with the accompanyingFigures.

FIG. 1 illustrates a cross-section view of a device 100 in accordancewith an embodiment. The device 100 includes a cap 102 and a substrate104 bonded or coupled to the cap 102. In the device 100, an enclosure112 is formed between the cap 102 and the substrate 104. In oneembodiment, the enclosure 112 is formed with a desired gas and at adesired pressure by any of wafer fusion bonding, eutectic bonding,thermal compression bonding, epoxy, and other bonding methods. In oneembodiment, the cap 102 (cap wafer) includes a MEMS device within theenclosure 112 and the substrate 104 is a complementarymetal-oxide-semiconductor (CMOS) substrate (CMOS circuit wafer).

In one embodiment, the cap 102 comprises a handle wafer 102 a, a MEMSdevice wafer 102 b, and a seal ring 102 c which interfaces with thesubstrate 104. In another embodiment, the cap 102 comprises a differentset of parts. The enclosure 112 contains a material 108 which changesthe pressure within the enclosure 112 when heated (e.g., heated using alaser). In one embodiment, the material 108 is deposited on a layer 110that is integrated within or into the substrate 104.

In one embodiment, the material 108 is an outgas sing material whichoutgasses when heated thereby increasing the pressure within theenclosure 112. In another embodiment, the material 108 is a getteringmaterial which absorbs gas when heated thereby decreasing the pressurewithin the enclosure 112. In another embodiment, the material 108comprises both an outgas sing material portion and a gettering materialportion so that when either portion of the material 108 is heated, thecavity pressure can be changed accordingly (based upon which portion isheated). In one embodiment, the outgassing material is a silicon oxideincluding but not limited to tetraethyl orthosilicate (TEOS) or highdensity plasma (HDP) deposited silicon dioxide.

In FIG. 1, a method for changing the pressure within the enclosure 112can include applying and focusing a laser light 106 through the cap 102and onto the material 108. In one embodiment, the laser light 106 has aninfrared (IR) wavelength that enables it to partially or substantiallypass through the cap 102. In one embodiment, the material 108 isdeposited on the layer 110 that comprises a metal layer so that thelayer 110 partially reflects the incident laser light from the appliedlaser light 106 back onto the material 108 (further heating the material108).

If the material 108 is an outgassing material, the laser light 106 thatis focused on the material 108 and the reflections from the laser light106 that are reflected by the layer 110 and back onto the material 108increase the energy within the outgassing material. Once the energywithin the outgas sing material is increased and the temperature of theoutgas sing material increases sufficiently, the outgas sing materialreleases gases, increasing the pressure within the enclosure 112. Inanother embodiment, the material 108 is a gettering material whichdecreases the enclosure 112 pressure when heated by the laser light 106.

FIG. 2 illustrates a cross-section view of a device 200 in accordancewith an embodiment. The device 200 includes a cap 202 and a substrate204 bonded or coupled to the cap 202. In the device 200, an enclosure212 is formed between the cap 202 and the substrate 204. In oneembodiment, the enclosure 212 is formed with a desired gas and at adesired pressure by any of wafer fusion bonding, eutectic bonding,thermal compression bonding, epoxy, and other bonding methods. In oneembodiment, the cap 202 (cap wafer) includes a MEMS device within theenclosure 212 and the substrate 204 is a complementarymetal-oxide-semiconductor (CMOS) substrate (CMOS circuit wafer).

In one embodiment, the cap 202 comprises a handle wafer 202 a, a MEMSdevice wafer 202 b, and a seal ring 202 c which interfaces with thesubstrate 204. In another embodiment, the cap 202 comprises a differentset of parts. The enclosure 212 contains a material reservoir 208 whichchanges the pressure within the enclosure 212 when heated (e.g., heatedusing a laser). The material reservoir 208 comprises additional materialin comparison to the material 108 of the device 100 in FIG. 1 and thisenables the device 200 to more readily change the pressure within theenclosure 212. In one embodiment, the material reservoir 208 isdeposited within a metal trough 210 that is integrated within or intothe substrate 204. The metal trough 210 reflects the incident laserlight 206 that is applied to the material reservoir 208 to further heatup the material reservoir 208 thereby further changing the pressurewithin the enclosure 212.

In one embodiment, the metal trough 210 is not connected to othercircuitry in order to thermally isolate the area around the metal trough210 from surrounding devices and MEMS structures. In another embodiment,the metal trough 210 is connected to an electrical ground to dissipatethe heat that is generated when the laser light 206 is applied throughthe enclosure 212 and onto the material reservoir 208. The device 200provides for a greater concentration of laser energy and heat byincreasing the number of reflections that occur through the materialreservoir 208.

If the material reservoir 208 is an outgas sing material, the laserlight 206 that is focused on the material reservoir 208 and thereflections from the laser light 206 that are reflected by the metaltrough 210 and back onto the material reservoir 208 increase the energywithin the outgassing material. Once the energy within the outgassingmaterial is increased and the temperature of the outgassing materialincreases sufficiently, the outgas sing material releases gases therebyincreasing the pressure within the enclosure 212.

In another embodiment, the material reservoir 208 is a getteringmaterial which decreases the enclosure 212 pressure when heated by thelaser light 206. The metal trough 210 helps to reflect incident laserlight and heat up the gettering material of the material reservoir 208which absorbs gases within the enclosure 212 thereby decreasing thepressure within the enclosure 212. In another embodiment, an enclosurecontains both an outgassing material and a gettering material depositedin different areas within the same enclosure.

FIG. 3 illustrates a cross-section view of a device 300 in accordancewith an embodiment. The device 300 includes a cap 302 and a substrate304 bonded or coupled to the cap 302. In the device 300, a firstenclosure 312 and a second enclosure 314 are formed between the cap 302and the substrate 304. In another embodiment, more than two sealedcavities or enclosures are formed in the device 300. In one embodiment,each of the first and the second enclosures 312 and 314 are formed witha desired gas and at a desired pressure by any of wafer fusion bonding,eutectic bonding, thermal compression bonding, epoxy, and other bondingmethods. In one embodiment, the cap 302 (cap wafer) includes a MEMSdevice within either or both of the first and the second enclosures 312and 314 and the substrate 304 is a complementarymetal-oxide-semiconductor (CMOS) substrate (CMOS circuit wafer).

In one embodiment, the cap 302 comprises a handle wafer 302 a, a MEMSdevice wafer 302 b, and a seal ring 302 c which interfaces with thesubstrate 304. In another embodiment, the cap 302 comprises a differentset of parts. In one embodiment, the first enclosure 312 contains amaterial 308 which changes the pressure within the enclosure 312 whenheated (e.g., heated using a laser). In another embodiment, the secondenclosure 314 contains the material 308. In another embodiment, both thefirst and the second enclosures 312 and 314 contain the material 308 intwo separate portions. In another embodiment, an enclosure contains bothan outgassing material and a gettering material deposited in differentareas within the same enclosure. In one embodiment, the material 308 isdeposited on a layer 310 that is integrated within or into the substrate304.

In the device 300, the first and the second enclosures 312 and 314 aresealed at the same time and under the same process conditions. Aftersealing, the enclosure or cavity pressure can be selectively alteredwithin each of the first and the second enclosures 312 and 314 byapplying varying amounts of a laser light 306 (or another heat producingmechanism). In one embodiment, and as aforementioned, once the laserlight 306 is applied to the material 308, and the layer 310 (metallayer) reflects the laser light and heat back to the material 308, thematerial 308 will heat up.

If the material 308 is an outgas sing material then the heating up willresult in outgassing (releasing of gases) into the first enclosure 312thereby increasing the pressure within the first enclosure 312. If thematerial 308 is a gettering material then the heating up will result inabsorption of gases from the first enclosure 312 thereby decreasing thepressure within the first enclosure 312.

In FIG. 3, the second enclosure does not include a material andtherefore the laser light 306 is not applied through the cap 302 andinto the second enclosure 314. As a result, only the pressure of thefirst enclosure 312 will increase (or decrease) and the pressure of thesecond enclosure 314 will be the same pressure as originally sealed. Ifthe pressure of the first enclosure 312 is increased (because thematerial 308 is outgassing) then the pressure of the second enclosure314 would be lower than the pressure of the first enclosure 312. If thepressure of the first enclosure 312 is decreased (because the material308 is a getter material) then the pressure of the second enclosure 314would be higher than the pressure of the first enclosure 312.

The device 300 is optimal for MEMS devices with a cap 302 and asubstrate 304 that contain different MEMS elements that function best atdifferent pressures. For example, with inertial sensors it is beneficialto have a lower pressure the MEMS gyroscope operation but it isbeneficial to have a higher pressure for the MEMS accelerometeroperation. The method in accordance with the present invention enablesprecise and customizable tuning of the pressures within each enclosureto individually optimize performance for one MEMS element in a firstcavity (e.g., accelerometer in the first enclosure 312 that requires ahigher pressure) and for another MEMS element in a second cavity (e.g.,gyroscope in the second enclosure 314 that requires a lower pressure sothe originally sealed pressure is maintained).

FIG. 4 illustrates a cross-section view of a device 400 in accordancewith an embodiment. The device 400 includes a cap 402 and a substrate404 bonded or coupled to the cap 402. In the device 400, a firstenclosure 412 and a second enclosure 414 are formed between the cap 402and the substrate 404. In another embodiment, more than two sealedcavities are formed in the device 400. In one embodiment, each of thefirst and the second sealed cavities 412 and 414 are formed with adesired gas and at a desired pressure by any of wafer fusion bonding,eutectic bonding, thermal compression bonding, epoxy, and other bondingmethods. In one embodiment, the cap 402 (cap wafer) includes a MEMSdevice within either or both of the first and the second sealed cavities412 and 414 and the substrate 404 is a complementarymetal-oxide-semiconductor (CMOS) substrate (CMOS circuit wafer).

In one embodiment, the cap 402 comprises a handle wafer 402 a, a MEMSdevice wafer 402 b, and a seal ring 402 c which interfaces with thesubstrate 404. In another embodiment, the cap 402 comprises a differentset of parts. In one embodiment, the first enclosure 412 contains amaterial 408 which changes the pressure within the enclosure 412 whenheated (e.g., heated using a laser). In another embodiment, the secondenclosure 414 contains the material 408. In another embodiment, both thefirst and the second sealed cavities 412 and 414 contain the material408 in two separate portions. In one embodiment, the material 408 isdeposited on or integrated within or into the substrate 404. In anotherembodiment, an enclosure contains both an outgassing material and agettering material deposited in different areas within the sameenclosure.

In the device 400, the first and the second sealed cavities 412 and 414are sealed at the same time and under the same process conditions. Aftersealing, the enclosure or cavity pressure can be selectively alteredwithin each of the first and the second enclosures 412 and 414 byapplying varying amounts of a laser light 404. In one embodiment, and asaforementioned, once the laser light 404 is applied to the material 408,the material 408 will heat up.

If the material 408 is an outgas sing material then the heating up willresult in outgassing (releasing of gases) into the first enclosure 412thereby increasing the pressure within the first enclosure 412. If thematerial 408 is a gettering material then the heating up will result inabsorption of gases from the first enclosure 412 thereby decreasing thepressure within the first enclosure 412.

In FIG. 4, the second enclosure does not include an outgassing orgettering material and therefore the laser light 406 is not appliedthrough the cap 402 and into the second enclosure 414. As a result, onlythe pressure of the first enclosure 412 will increase (or decrease) andthe pressure of the second enclosure 414 will be the same pressure asoriginally sealed. If the pressure of the first enclosure 412 isincreased (because the material 408 is outgassing) then the pressure ofthe second enclosure 414 would be lower than the pressure of the firstenclosure 412. If the pressure of the first enclosure 412 is decreased(because the material 408 is a getter material) then the pressure of thesecond enclosure 414 would be higher than the pressure of the firstenclosure 412.

The main difference between the device 300 of FIG. 3 and the device 400of FIG. 4 is the presence of a layer 310 coupled to the material 308within the first enclosure 312 of FIG. 3 that is not present in FIG. 4(the material 408 is stand-alone within the first enclosure 412). Thelayer 310 (and any type of metal layer) reflects the laser light andincreases the heat that is applied onto the material that is within thefirst enclosure. In one embodiment, only an outgassing material isutilized as the material 308 in conjunction with the layer 310 of FIG. 3and only a gettering material is utilized as the material 408 of FIG. 4.

In one embodiment, the getter (gettering) metal includes but is notlimited to any of aluminum, magnesium, strontium, barium, calcium,zirconium, nickel, niobium, cesium, tantalum, titanium, thorium, cerium,lanthanum, cobalt, vanadium, and phosphorous. Once the heat is appliedto the getter material, the getter material is activated which causesany of absorption, adsorption, and a chemical reaction with gases withinthe sealed cavities and thereby decreases the pressure within the sealedcavities.

FIG. 5 illustrates a method 500 for changing a pressure within a devicein accordance with an embodiment. The method 500 comprises testing thedevice using a wafer level test, via step 502, and determining whetherpredetermined and preselected sites associated with the device meet atarget or desired pressure, via step 504. If the sites do not meet thetarget pressure, then the sites are illuminated with a laser (e.g., IRlaser), via step 506, to apply heat to a material within the device thatwhen heated changes the pressure within the device. Therefore, theheating of the material using the laser enables the site or sites thatdo not meet the target pressure to be tuned to meet the target pressure.After step 506, the method 500 returns back to step 502 to performadditional testing and determine whether the sites now meet the targetpressure. This feedback loop will continue until all of the sites withinthe device meet target pressures. Once all of the sites within thedevice meet the target pressures, the method 500 continues themanufacturing process associated with the device, via step 508.

The method 500 can be applied during the testing of electrical, optical,mechanical, or other properties within sealed cavities of MEMS devicesand other devices. In the method 500, a wafer with at least oneenclosure undergoes an initial wafer level test and if the pressurewithin the at least one enclosure does not meet the target pressurevalue, the pressure can be increased (or decreased) by applying a laserlight (or other form of heat) to a material located within the at leastone enclosure of the device. The device will be subsequently andrepeatedly tested for pressure and performance and additional laserlight or heat can be applied until the target pressure values areachieved within the at least one enclosure. The method 500 provides aclosed loop feedback control to increase/decrease pressure to a desiredlevel within each enclosure of a device.

FIG. 6 illustrates a cross-section view of a device 600 in accordancewith an embodiment. The device 600 includes a cap 602 and a substrate604 bonded or coupled to the cap 602. In the device 600, an enclosure612 is formed between the cap 602 and the substrate 604. In oneembodiment, the enclosure 612 is formed with a desired gas and at adesired pressure by any of wafer fusion bonding, eutectic bonding,thermal compression bonding, epoxy, and other bonding methods. In oneembodiment, the cap 602 (cap wafer) includes a MEMS device within theenclosure 612 and the substrate 604 is a complementarymetal-oxide-semiconductor (CMOS) substrate (CMOS circuit wafer).

In one embodiment, the cap 602 comprises a handle wafer 602 a, a MEMSdevice wafer 602 b, and a seal ring 602 c which interfaces with thesubstrate 604. In another embodiment, the cap 602 comprises a differentset of parts. The enclosure 612 contains a material 608 which changesthe pressure within the enclosure 612 when heated (e.g., heated using alaser). In one embodiment, the material 608 is deposited or grown on thecap 602. It may be advantageous to deposit an outgas sing or gettermaterial on the cap 602 if the material is not compatible withfabrication of the substrate 604, for example if the substrate 604 is aCMOS circuit wafer.

In one embodiment, the material 608 is an outgas sing material thatincreases the pressure within the enclosure 612 when heated by the laserlight 606. In another embodiment, the material 608 is a getteringmaterial that decreases the pressure within the enclosure 612 whenheated by the laser light 606. In another embodiment, both outgassingand getter materials are deposited on the cap 602 in different areas butwithin the same enclosure 612. The device 600 enables for the increaseor reduction of pressure as desired to meet target pressure levels.

In the described embodiments, the laser can be applied either from thecap 102, 202, 302, 402 and 602 or from the substrate 104, 204, 304, and604.

A method and system for changing a pressure in a device are disclosed.In one embodiment, the device is a MEMS device. The method comprisesapplying heat through one of at least two substrates onto a material ofthe device which changes the pressure within at least one enclosure whenexposed to the heat, wherein the at least one enclosure is formed by theat least two substrates. In one embodiment, the method applies the heatby using a laser. In one embodiment, the laser is an infrared (IR)laser. In one embodiment, the material of the device comprises any of anoutgassing material and a gettering material.

In one embodiment, the outgassing material comprises a silicon oxidecompound. In one embodiment, the gettering material comprises any oftitanium, a titanium compound, zirconium, a zirconium compound,aluminum, magnesium, strontium, barium, calcium, nickel, niobium,cesium, tantalum, thorium, cerium, lanthanum, cobalt, vanadium, andphosphorous. In one embodiment, the at least one enclosure includes ametal trough for holding the material there within. In one embodiment,the material comprises a plurality of interlayer dielectrics (ILDs)within the metal trough. In one embodiment, the device further includesa metal layer that has been integrated or coupled to one or both of theat least two substrates and the material is deposited onto the metallayer, wherein the metal layer prevents further transmission of thelaser thereby preventing further heating of the material. The metallayer is a portion of the metal trough that prevents furthertransmission of the laser.

In one embodiment, the at least one enclosure of the device is formed bycoupling or bonding together a MEMS substrate and a complementarymetal-oxide-semiconductor (CMOS) substrate. In one embodiment, thematerial is disposed on any of the MEMS substrate and the CMOSsubstrate.

In one embodiment, the method comprises applying the laser in a repeatedmanner to change the pressure within the at least one enclosure. In oneembodiment, the method further includes measuring a pressure within theat least one enclosure and reapplying the laser to the material tochange the pressure within the at least one enclosure.

In another embodiment, the method further includes measuring a parameterindicative of the pressure within the at least one enclosure andreapplying the laser to the material to change the parameter. In oneembodiment, the parameter is any of Q characteristics of the device,damping characteristics of the device, acoustic characteristics of thedevice, heat transfer within the at least one enclosure, and soundvelocity of the device.

In one embodiment, the system is a device. In another embodiment, thesystem is a MEMS device. The device comprises a first substrate and asecond substrate coupled or bonded to the first substrate, wherein atleast one enclosure is formed by and located between the first and thesecond substrates. The device further comprises a metal layer withineither one of first substrate and the second substrate. The devicefurther comprises a material that is within the metal layer orvertically aligned over the metal layer. When the material is heated bya laser or another heating device, the material changes a pressurewithin the at least one enclosure. In one embodiment, the firstsubstrate is the MEMS substrate and the second substrate is a CMOSsubstrate. In another embodiment, the first substrate is the CMOSsubstrate and the second substrate is the MEMS substrate.

As above described, a method and system (e.g., MEMS device) inaccordance with the present invention enables dynamic changing of thepressure within cavities or enclosures of the MEMS device after thecavities have already been sealed. By integrating a material within thesealed cavities that are either made up of an outgas sing material or agettering material and by applying a laser or heat to the material, thepressure within the sealed cavities can be altered in accordance withproduct specifications and desired varied pressure levels between thecavities. If the material is outgassing, the pressure will be increasedas the heating of the material will release gases into the enclosure. Ifthe material is gettering, the pressure will be decreased as the heatingof the material will absorb gases from the enclosure.

The method and system in accordance with the present invention greatlyreduces the manufacturing process involved with creating a device (suchas a MEMS device) that includes a plurality of cavities that are each atdiffering pressure levels. Instead of having to manufacture each cavitywith a certain desired pressure level during the manufacturing processand before cavity sealing (which adds complexity, time, and cost), theplurality of cavities can be manufactured and sealed all at the samepressure level and then the laser (or other form of heat) can be appliedselectively within each of the cavities to alter the pressure levels tothe desired target values.

Although the present invention has been described in accordance with theembodiments shown, one of ordinary skill in the art will readilyrecognize that there could be variations to the embodiments and thosevariations would be within the spirit and scope of the presentinvention. Accordingly, many modifications may be made by one ofordinary skill in the art without departing from the spirit and scope ofthe appended claims.

What is claimed is:
 1. A microelectromechanical systems (MEMS) device comprising: a first substrate; a second substrate bonded to the first substrate, wherein at least two enclosures are located between the first substrate and the second substrate; a metal layer within one of the first substrate and the second substrate; and a material vertically oriented over the metal layer, wherein the material is configured to change a pressure within at least one enclosure of the at least two enclosures in response to a laser heating of the material based at least in part on reflection of incident laser light from at least a portion of the metal layer to promote the laser heating of the material.
 2. The MEMS device of claim 1, wherein the metal layer comprises a portion of a metal trough that prevents further transmission of the laser.
 3. The MEMS device of claim 2, wherein the material comprises a plurality of interlayer dielectrics (ILDs) within the metal trough.
 4. The MEMS device of claim 1, wherein the material comprises an outgassing material.
 5. The MEMS device of claim 4, wherein the outgassing material comprises a dielectric.
 6. The MEMS device of claim 1, wherein the material comprises a gettering material.
 7. The MEMS device of claim 6, wherein the gettering material comprises at least one of titanium, a titanium compound, zirconium, a zirconium compound, aluminum, magnesium, strontium, barium, calcium, nickel, niobium, cesium, tantalum, titanium, thorium, cerium, lanthanum, cobalt, vanadium, or phosphorous.
 8. The MEMS device of claim 1, wherein the first substrate is a MEMS substrate and the second substrate is a complementary metal-oxide-semiconductor (CMOS) substrate.
 9. The MEMS device of claim 8, wherein the material is disposed on any of the MEMS substrate and the CMOS substrate.
 10. A device comprising: a microelectromechanical systems (MEMS) substrate; a complementary metal-oxide-semiconductor (CMOS) substrate bonded to the MEMS substrate, wherein the MEMS substrate and the CMOS substrate define a plurality of enclosures disposed within the device; a first material disposed within at least one enclosure of the plurality of enclosures, wherein the first material is configured to change pressure of at least one enclosure of the plurality of enclosures in response to laser heating of the first material; and a second material adjacent to the first material, wherein the second material is configured to reflect incident laser light to promote the laser heating of the first material.
 11. The device of claim 10, wherein the second material comprises a metal layer associated with at least one of the MEMS substrate or the CMOS substrate.
 12. The device of claim 10, wherein the first material comprises an outgassing material comprising at least one of a silicon oxide compound or a dielectric material.
 13. The device of claim 10, wherein the first material comprises a gettering material that comprises at least one of titanium, a titanium compound, zirconium, a zirconium compound, aluminum, magnesium, strontium, barium, calcium, nickel, niobium, cesium, tantalum, thorium, cerium, lanthanum, cobalt, vanadium, or phosphorous.
 14. The device of claim 10, wherein the first material comprises a plurality of interlayer dielectrics (ILDs) within a metal trough associated with at least one of the MEMS substrate or the CMOS substrate.
 15. The device of claim 10, wherein the first material is adjacent to the MEMS substrate.
 16. The device of claim 10, wherein the first material is adjacent to the CMOS substrate.
 17. The device of claim 10, further comprising: at least one MEMS structure disposed within at least one enclosure of the plurality of enclosures.
 18. A device, comprising: a first substrate; a second substrate; a means for bonding the first substrate to the second substrate, wherein the first substrate and the second substrate define at least one enclosure; a means for changing pressure within the at least one enclosure upon laser heating by exposure to a laser; a means for receiving incident light of the laser through at least one of the first substrate or the second substrate; and a means for reflecting incident laser light back onto the means for changing pressure.
 19. The device of claim 18, wherein the first substrate comprises a microelectromechanical systems (MEMS) substrate, wherein the second substrate comprises a complementary metal-oxide-semiconductor (CMOS) substrate, and wherein the means for reflecting incident laser light comprises a metal layer of at least one other of the first substrate or the second substrate. 